Comparison of 3DCRT and IMRT out-of-field doses in pediatric patients using Monte Carlo simulations with treatment planning system calculations and measurements

Frontiers in Oncology

Oncology

Bryan P. Bednarz¹  Pedro Almeida²  Pedro Vaz³  Ana Cravo Sá⁴  Andreia Barateiro⁵  Tiago Madaleno⁵ 

[1] Department of Medical Physics, Wisconsin Institutes for Medical Research, University of Wisconsin Hospital and Clinics, Madison, WI, United States;Instituto de Biofísica e Engenharia Biomédica, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal;Radiation Protection and Safety Group, Centro de Ciências e Tecnologias Nucleares (C2TN), Bobadela, Portugal;Radiation Protection and Safety Group, Centro de Ciências e Tecnologias Nucleares (C2TN), Bobadela, Portugal;Diagnostic, Therapeutic and Public Health Sciences Department, Escola Superior de Tecnologia da Saúde de Lisboa (ESTeSL), Lisbon, Portugal;Instituto de Biofísica e Engenharia Biomédica, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal;Radiotherapy Department, Portuguese Institute of Oncology Francisco Gentil, Lisbon, Portugal;

关键词: radiotherapy planning;    out-of-field dose;    pediatric tumors;    Monte Carlo simulations;    computational voxel phantoms;    IMRT;    3DCRT;   

DOI  :  10.3389/fonc.2022.879167

 received in 2022-02-18, accepted in 2022-07-04,  发布年份 2022

来源: Frontiers

【 摘 要 】

3DCRT and IMRT out-of-field doses in pediatric patients were compared using Monte Carlo simulations with treatment planning system calculations and measurements.PurposeOut-of-field doses are given to healthy tissues, which may allow the development of second tumors. The use of IMRT in pediatric patients has been discussed, as it leads to a “bath” of low doses to large volumes of out-of-field organs and tissues. This study aims to compare out-of-field doses in pediatric patients comparing IMRT and 3DCRT techniques using measurements, Monte Carlo (MC) simulations, and treatment planning system (TPS) calculations.Materials and methodsA total dose of 54 Gy was prescribed to a PTV in the brain of a pediatric anthropomorphic phantom, for both techniques. To assess the out-of-field organ doses for both techniques, two treatment plans were performed with the 3DCRT and IMRT techniques in TPS. Measurements were carried out in a LINAC using a pediatric anthropomorphic phantom and thermoluminescent dosimeters to recreate the treatment plans, previously performed in the TPS. A computational model of a LINAC, the associated multileaf collimators, and a voxelized pediatric phantom implemented in the Monte Carlo N-Particle 6.1 computer program were also used to perform MC simulations of the out-of-field organ doses, for both techniques.ResultsThe results obtained by measurements and MC simulations indicate a significant increase in dose using the IMRT technique when compared to the 3DCRT technique. More specifically, measurements show higher doses with IMRT, namely, in right eye (13,041 vs. 593 mGy), left eye (6,525 vs. 475 mGy), thyroid (79 vs. 70 mGy), right lung (37 vs. 28 mGy), left lung (27 vs. 20 mGy), and heart (31 vs. 25 mGy). The obtained results indicate that out-of-field doses can be seriously underestimated by TPS.DiscussionThis study presents, for the first time, out-of-field dose measurements in a realistic scenario and calculations for IMRT, centered on a voxelized pediatric phantom and an MC model of a medical LINAC, including MLC with log file-based simulations. The results pinpoint significant discrepancies in out-of-field doses for the two techniques and are a cause of concern because TPS calculations cannot accurately predict such doses. The obtained doses may presumably increase the risk of development of second tumors.

【 授权许可】

Unknown   
Copyright © 2022 Sá, Barateiro, Bednarz, Almeida, Vaz and Madaleno